'\" t
.\"     Title: ALTER DOMAIN
.\"    Author: The PostgreSQL Global Development Group
.\" Generator: DocBook XSL Stylesheets v1.75.2 <http://docbook.sf.net/>
.\"      Date: 2011-12-01
.\"    Manual: PostgreSQL 9.1.2 Documentation
.\"    Source: PostgreSQL 9.1.2
.\"  Language: English
.\"
.TH "ALTER DOMAIN" "7" "2011-12-01" "PostgreSQL 9.1.2" "PostgreSQL 9.1.2 Documentation"
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.SH "NAME"
ALTER_DOMAIN \- change the definition of a domain
.\" ALTER DOMAIN
.SH "SYNOPSIS"
.sp
.nf
ALTER DOMAIN \fIname\fR
    { SET DEFAULT \fIexpression\fR | DROP DEFAULT }
ALTER DOMAIN \fIname\fR
    { SET | DROP } NOT NULL
ALTER DOMAIN \fIname\fR
    ADD \fIdomain_constraint\fR
ALTER DOMAIN \fIname\fR
    DROP CONSTRAINT \fIconstraint_name\fR [ RESTRICT | CASCADE ]
ALTER DOMAIN \fIname\fR
    OWNER TO \fInew_owner\fR
ALTER DOMAIN \fIname\fR
    SET SCHEMA \fInew_schema\fR
.fi
.SH "DESCRIPTION"
.PP

ALTER DOMAIN
changes the definition of an existing domain\&. There are several sub\-forms:
.PP
SET/DROP DEFAULT
.RS 4
These forms set or remove the default value for a domain\&. Note that defaults only apply to subsequent
INSERT
commands; they do not affect rows already in a table using the domain\&.
.RE
.PP
SET/DROP NOT NULL
.RS 4
These forms change whether a domain is marked to allow NULL values or to reject NULL values\&. You can only
SET NOT NULL
when the columns using the domain contain no null values\&.
.RE
.PP
ADD \fIdomain_constraint\fR
.RS 4
This form adds a new constraint to a domain using the same syntax as
CREATE DOMAIN (\fBCREATE_DOMAIN\fR(7))\&. This will only succeed if all columns using the domain satisfy the new constraint\&.
.RE
.PP
DROP CONSTRAINT
.RS 4
This form drops constraints on a domain\&.
.RE
.PP
OWNER
.RS 4
This form changes the owner of the domain to the specified user\&.
.RE
.PP
SET SCHEMA
.RS 4
This form changes the schema of the domain\&. Any constraints associated with the domain are moved into the new schema as well\&.
.RE
.PP
You must own the domain to use
ALTER DOMAIN\&. To change the schema of a domain, you must also have
CREATE
privilege on the new schema\&. To alter the owner, you must also be a direct or indirect member of the new owning role, and that role must have
CREATE
privilege on the domain\*(Aqs schema\&. (These restrictions enforce that altering the owner doesn\*(Aqt do anything you couldn\*(Aqt do by dropping and recreating the domain\&. However, a superuser can alter ownership of any domain anyway\&.)
.SH "PARAMETERS"
.PP
.PP
\fIname\fR
.RS 4
The name (possibly schema\-qualified) of an existing domain to alter\&.
.RE
.PP
\fIdomain_constraint\fR
.RS 4
New domain constraint for the domain\&.
.RE
.PP
\fIconstraint_name\fR
.RS 4
Name of an existing constraint to drop\&.
.RE
.PP
CASCADE
.RS 4
Automatically drop objects that depend on the constraint\&.
.RE
.PP
RESTRICT
.RS 4
Refuse to drop the constraint if there are any dependent objects\&. This is the default behavior\&.
.RE
.PP
\fInew_owner\fR
.RS 4
The user name of the new owner of the domain\&.
.RE
.PP
\fInew_schema\fR
.RS 4
The new schema for the domain\&.
.RE
.SH "NOTES"
.PP
Currently,
ALTER DOMAIN ADD CONSTRAINT
and
ALTER DOMAIN SET NOT NULL
will fail if the named domain or any derived domain is used within a composite\-type column of any table in the database\&. They should eventually be improved to be able to verify the new constraint for such nested columns\&.
.SH "EXAMPLES"
.PP
To add a
NOT NULL
constraint to a domain:
.sp
.if n \{\
.RS 4
.\}
.nf
ALTER DOMAIN zipcode SET NOT NULL;
.fi
.if n \{\
.RE
.\}
.sp
To remove a
NOT NULL
constraint from a domain:
.sp
.if n \{\
.RS 4
.\}
.nf
ALTER DOMAIN zipcode DROP NOT NULL;
.fi
.if n \{\
.RE
.\}
.PP
To add a check constraint to a domain:
.sp
.if n \{\
.RS 4
.\}
.nf
ALTER DOMAIN zipcode ADD CONSTRAINT zipchk CHECK (char_length(VALUE) = 5);
.fi
.if n \{\
.RE
.\}
.PP
To remove a check constraint from a domain:
.sp
.if n \{\
.RS 4
.\}
.nf
ALTER DOMAIN zipcode DROP CONSTRAINT zipchk;
.fi
.if n \{\
.RE
.\}
.PP
To move the domain into a different schema:
.sp
.if n \{\
.RS 4
.\}
.nf
ALTER DOMAIN zipcode SET SCHEMA customers;
.fi
.if n \{\
.RE
.\}
.SH "COMPATIBILITY"
.PP

ALTER DOMAIN
conforms to the
SQL
standard, except for the
OWNER
and
SET SCHEMA
variants, which are
PostgreSQL
extensions\&.
.SH "SEE ALSO"
CREATE DOMAIN (\fBCREATE_DOMAIN\fR(7)), DROP DOMAIN (\fBDROP_DOMAIN\fR(7))
